Position sensors that sense a change in position of a movable member and provide a corresponding input signal to an electrical controller have many applications. The displacement of movable acceleration and brake pedals on electric vehicles for example has in the past been detectable with an electrical resistance that varies in some proportion to the displacement, which corresponds to a predetermined degree of acceleration or braking desired by an operator. The variable resistance, like a potentiometer or other variable device, is generally mechanically linked with the movable member to sense displacement over a predetermined range of motion. To sense the position of an electric vehicle acceleration or brake pedal, it has been suggested to rotate a potentiometer shaft with an arm extending from the pedal and coupled to a lever extending from the potentiometer shaft. Linkage of the position sensor with the movable member however usually requires custom fabrication of an appropriate length arm between the pedal and the potentiometer. In addition, the position sensor initially must be calibrated to provide a specified range of resistance over the detectable range of motion. Calibration of the sensor moreover is a laborious procedure in part dependent upon proper linkage between the pedal and the potentiometer. Linkage and calibration are further complicated by the fact that some electric vehicles have adjustable accelerator and brake pedals to accommodate the physical stature of the vehicle operator, which affects the required linkage between the pedal and the position sensor.
Some applications require actuation of an electrical switch by the movable member somewhere in its range of motion. In the electric vehicle application for example it is sometimes desirable to actuate a switch so as to provide battery power to an electrical system controller upon depression of the accelerator pedal to some degree during its initial range of motion whereafter the position sensor varies the resistance in correspondence with the position of the movable member so as to control acceleration. Other applications require actuation of a switch when the movable member is at the end of its range of motion, or alternatively at some intermediate point in its range of motion. The switch generally requires a separate mechanical linkage to the movable member or to the potentiometer so as to actuate the switch at the appropriate position of the movable member during its range of motion, which complicates installation and increases costs. The linkage of the switch with the potentiometer further complicates the calibration of the position sensor since it is often critical to properly sequence or accurately time the occurrence of switch actuation and variation of resistance. In electric vehicles for instance the switch must be actuated before any variation of resistance beyond some resistance threshold so as to ensure safe operation of the vehicle. Similar operational constraints may be required in other applications.
In view of the discussion above, there exists a demonstrated need for an advancement in the art of actuating an electrical switch and varying electrical resistance usable for sensing displacement of a movable member.